Control of transcription of the growth hormone (GH) gene in GH3 cells and GH3 x L cell hybrids has been studied. GH induction by glucocorticoid in GH3 cells is not blocked by cycloheximide. In GH3 x L cell hybrids, and in GH3 subclones, there is correlation between GH expression and methylation at a specific Tha I site 5'-wards of the initiation start site of GH gene transcription. GH gene regions have been joined to the chloramphenicol acetyl transferase (CAT) gene and the hybrid genes are being transfected into cells to test for control by hormones. A new system for studying DNA-steroid receptor interactions on agarose gels is being developed. In the IM9 and CEM human leukemic cell lines, glucocorticoid effects and glucocorticoid receptors have been studied. Many physical and immunological parameters of the human leukemic cell glucocorticoid receptor have been established, from wild-type steroid-sensitive cells and several classes of steroid-resistant sublines. The phenylpyrazole-substituted steroid cortivazol has been found to have two binding sites in wild-type cells but only one in "receptorless" cells. A cDNA library from CEM C7 cells is being prepared. An expression library of cDNAs from IM9 cells has been prepared and is being screened with our anti-human glucocorticoid receptor (HGR) antiserum. Immunocytochemical methods for examining HGRs have been developed. Preliminary examination of tyrosine aminotransferase genes in highly steroid sensitive vs less sensitive rat hepatoma cell lines suggest that the gene may be in different configurations in the two.